The present invention relates to combustion turbine power plants utilizing solar energy to increase their capacity and efficiency.
Combustion turbine power plants can be brought on line quickly to meet peak demands for electric power. The demand for power in warmer climates generally is greater during the day when temperatures are higher and solar energy is available.
Various schemes have been proposed, therefore, for making use of solar energy in a combustion turbine power plant for improving its heat rate (fuel usage per unit electric energy output, typically measured in Btu's per kWh) and/or its power capacity, to reduce the cost of supplying electric power to satisfy peak demand. For example, it has been proposed to utilize solar energy to heat air supplied from the turbine's air compressor before it is introduced into its combustion chamber.
This scheme has several serious drawbacks which result in reduced plant capacity and efficiency. Heating the inlet air to the combustor of a gas turbine decreases the air's density, which reduces the power output. More serious constraints on gas turbine output are imposed by the strict temperature limits which must be observed to avoid premature failure of critical components. Increasing inlet air temperature requires a concomitant decrease in the rate at which air and fuel are supplied to the gas turbine in order to avoid exceeding such temperature limits, resulting in reduced power output. However, gas turbine parasitic losses increase as a percentage of gross output when the latter decreases, leading to higher specific fuel consumption. This proposal if implemented, therefore, would not serve its intended purpose.
Another scheme would add heat to combustion gases by means of solar energy. However, the solar energy collection system would then need to operate at very high temperatures and pressures, since it would need to augment the energy content of combustion gases which are already at high temperature and pressure. The solar collection system thus would require a high capital investment, and would suffer large parasitic heat losses due to the high temperatures at which it would operate.